Communication Device for Detecting Transmission of an Improper Message to a Network

1. A communication device comprising: a controller configured for: transmitting and receiving a message attached with a priority level via a communication line, and arbitrating, in a case where message transmission from the communication device and message transmission from a different device are concurrently performed, to decide which message transmission is to be performed based on the priority level; a counter in which the number of consecutive blocks, which corresponds to the number of messages consecutively blocked from being transmitted as a result of arbitration by the controller, is stored; and a memory in which the number of allowed blocks, which corresponds to the number of consecutive messages allowed to be blocked, is stored in association with the priority level, wherein the controller is further configured for: detecting abnormality concerning communication based on the number of consecutive blocks stored in the counter and the number of allowed blocks stored in the memory, for each message to be transmitted or received by the controller, and determining, in a case where the controller receives a message, whether or not the number of consecutive blocks stored in the counter is larger than the number of allowed blocks stored in the memory in accordance with the priority level attached to the message.

2. The communication device according to claim 1 , wherein the controller is further configured to determine, every time a message is to be transmitted from the controller, whether or not the number of consecutive blocks stored in the counter is larger than the number of allowed blocks stored in the memory in accordance with the priority level attached to the message, and detect that abnormality concerning communication occurs at a time point when it is determined that the number of consecutive blocks is larger than the number of allowed blocks.

3. The communication device according to claim 1 , further comprising: a second counter in which the accumulated number of bits in a message transmitted or received on the communication line is stored, wherein the controller is further configured for detecting abnormality concerning communication based on the accumulated number during a predetermined period of time.

4. The communication device according to claim 1 , further comprising a control unit performing such control as to fix a potential of the communication line if the controller detects abnormality.

5. The communication device according to claim 1 , further comprising a notification unit notifying a different device, if the controller detects abnormality, via a signal line different from the communication line.